This invention concerns a biocidal material containing a specific mixture of biocides, and a method for the treatment of an aqueous solution in which micro-organisms are liable to grow, that makes use of the material of this invention.
In industry the growth of micro-organisms in aqueous solutions is a known phenomenon that requires the use of biocides. Biocides act to inhibit the growth and (or) proliferation of micro-organisms. In particular, in the field of photography it is known that when the growth of micro-organisms goes unchecked the aqueous solutions turns into a slurry, clogging equipment, spoiling processing baths and impairing the quality of photographic images.
For environmental safety it is desirable to reduce the quantity of biocide necessary to inhibit the growth of micro-organisms. Too much biocide in effluent is unacceptable when these effluents are to be processed in wastewater treatment plants.
Many publications describe biocide mixtures. For example patent application WO 99/08530 describes a specific mixture of biocides containing a 2-methylisothiazolin-3-one compound and a 1,2-benzisothiazolin-3-one compound, compositions containing a 5-chloro-2-methylisothiazolin-3-one being excluded. This type of composition affords a synergistic biocidal effect.
Patent application EP 897 666 describes a solid biocide composition that allows the rate of release of the biocide into a solution to be reduced.
U.S. Pat. No. 4 552 752 describes a biocidal article for use in aqueous media that comprises a finely-divided water-insoluble support in which is absorbed a water-soluble biocide.
It is desirable to have a new biocidal material that allows the quantities of biocide necessary to inhibit the growth of micro-organisms to be reduced, and that remains active for several weeks.
This invention concerns a biocidal material that comprises a water-permeable matrix in which is dispersed a mixture of biocides at least one of which is a hydrophilic biocide and at least one other of which is a hydrophobic biocide. The invention concerns further a device to deliver a controlled quantity of biocide into an aqueous solution where growth of microorganisms is liable to occur.
The biocidal material of the invention displays improved efficacy. It allows a marked reduction in the quantity of biocides needed to inhibit micro-organisms. Additionally the biocidal material of the invention can be used for many weeks throughout which time it retains its biocidal activity.